July 1, 2013 at 3:58 pm
Hi all,
I have a tricky one.
I have a dataset as below which deals with airport delays.
CREATE TABLE #delaystats
(
airport VARCHAR(10)
,thedate SMALLDATETIME
,delay1 INT
,delay2 INT
,delay3 INT
,delay4 INT
,delay5 INT
)
INSERT INTO #delaystats (airport,thedate,delay1,delay2,delay3,delay4,delay5)
SELECT 'LAX', '01-May-2013',2,0,1,4,1 UNION ALL
SELECT 'LAX', '02-May-2013',0,0,1,2,0 UNION ALL
SELECT 'LAX', '03-May-2013',0,0,0,2,0
SELECT * FROM #delaystats
DROP TABLE #delaystats
The dataset is quite simple and contains an airport code, date and field-names which represent flight delays. So delay1 contains a number representing how many flights where delays by 1 hour on that day, delay2 is 2 hours and so on.
What I need to do is for each date return the field that represents the minimum delay for that day. Note it is not how many flights where delayed but the minimum delay for that day.
So the result on the above dataset would be
Airport Date MinDelay
LAX 01-May-2013 Delay1
LAX 02-May-2013 Delay3
LAX 03-May-2013 Delay4
Any ideas on how to achieve this?
thanks,
derrysql
July 1, 2013 at 4:15 pm
How about:
select airport,
thedate,
case when delay1 <> 0 then 'delay1'
when delay2 <> 0 then 'delay2'
when delay3 <> 0 then 'delay3'
when delay4 <> 0 then 'delay4'
when delay5 <> 0 then 'delay5'
else 'no delays'
end as 'Min Delay'
from #delaystats
July 1, 2013 at 5:53 pm
I agree with David here, since it's a relatively simple paradigm and a direct order of evaluation you've got. Anything more complex would be overkill, as well as non optimal, since CASE can short circuit the evaluation once it's true.
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